Base station, terminal, and communication method

ABSTRACT

UEs each monitor a search space in multiple CORSETs and appropriately detect a DCI. In a base station ( 100 ), a DCI generator ( 102 ) selects one of multiple cases each indicating a combination of CORSETs to be monitored by a terminal ( 200 ) among multiple control channel regions (CORSETs). A transmitter ( 106 ) indicates, by higher-layer signaling, configuration information indicating the multiple cases, and indicates the selected case by dynamic signaling.

TECHNICAL FIELD

The present disclosure relates to a base station, a terminal, and acommunication method.

BACKGROUND ART

A communication system so called the fifth generation mobilecommunication system (5G) has been under study. In 5Q studies have beenconducted on flexibly providing functions respectively for use caseswhere communication traffic increases, where the number of terminals tobe connected increases, and where high reliability and/or low latency isrequired. There are three representative use cases, which are enhancedMobile Broadband (eMBB), massive Machine Type Communications (mMTC), andUltra Reliable and Low Latency Communications (URLLC). The 3rdGeneration Partnership Project (3GPP), which is an internationalstandardization organization, has been conducting studies on furtherevolution of the communication system from both aspects of furtherevolution of the LTE systems and New Radio Access Technology (RAT) (see,e.g., Non-Patent Literature (hereinafter, referred to as “NPL”) 1).

CITATION LIST Non-Patent Literature

NPL 1

-   RP-161596, “Revision of SI: Study on New Radio Access Technology,”    NTT DOCOMO, September 2016

NPL 2

-   R1-1702764, “Discussion on group common PDCCH”, Panasonic, February    2017

SUMMARY OF INVENTION

In New RAT, studies have been carried out on configuring a terminal(User Equipment: UE) with multiple control resource sets (hereinafter,referred to as “CORSETs”) as a Physical Downlink Control Channel (PDCCH)region, which is a control signal channel where a downlink controlindicator (DCI) is mapped. In New RAT, however, studies on a method inwhich a UE monitors (blind decoding) a search space in multiple CORSETsand detects a DCI have not been carried out enough.

One non-limiting and exemplary embodiment of this disclosure facilitatesproviding a base station, a terminal, and a communication method eachallowing a UE to monitor a search space in multiple CORSETs and toappropriately detect a DCI.

A base station according to an aspect of the present disclosureincludes: circuitry, which, in operation, selects one of a plurality ofcases each indicating a combination of control channel regions to bemonitored by a terminal among a plurality of control channel regions;and a transmitter, which in operation, indicates, by higher-layersignaling, configuration information indicating the plurality of cases,and indicates the selected case by dynamic signaling.

A terminal according to an aspect of the present disclosure includes: areceiver, which in operation, receives higher-layer signaling containingconfiguration information indicating a plurality of cases eachindicating a combination of control channel regions to be monitored bythe terminal among a plurality of control channel regions, and receivesdynamic signaling indicating one of the plurality of cases; andcircuitry, which, in operation, detects control information directed tothe terminal in the control channel region corresponding to the one caseindicated by the dynamic signaling among the plurality of cases.

A communication method according to an aspect of this disclosureincludes: selecting one of a plurality of cases each indicating acombination of control channel regions to be monitored by a terminalamong a plurality of control channel regions; and indicating, byhigher-layer signaling, configuration information indicating theplurality of cases, and indicating the selected case by dynamicsignaling.

A communication method according to an aspect of this disclosureincludes: receiving higher-layer signaling containing configurationinformation indicating a plurality of cases each indicating acombination of control channel regions to be monitored by a terminalamong a plurality of control channel regions, and receiving dynamicsignaling indicating one of the plurality of cases; and detectingcontrol information directed to the terminal in the control channelregion corresponding to the one case indicated by the dynamic signalingamong the plurality of cases.

Note that the comprehensive or specific aspects mentioned above may beimplemented by a system, an apparatus, a method, an integrated circuit,a computer program or a recoding medium, or any combination of thesystem, the apparatus, the method, the integrated circuit, the computerprogram, and the recoding medium.

According to an aspect of this disclosure, a UE monitors a search spacein multiple CORSETs and can appropriately detect a DCI.

The specification and the drawings make it clear more advantages andeffects in an aspect of this disclosure. Such advantages and/or effectsare provided by the features disclosed in some embodiments as well asthe specification and the drawings, but all of them do not have to beprovided in order to obtain one or more identical features.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a diagram illustrating a configuration example of CORSETs;

FIG. 1B is a diagram illustrating another configuration example of theCORSETs;

FIG. 2 is a block diagram illustrating part of a configuration of a basestation according to Embodiment 1;

FIG. 3 is a block diagram illustrating part of a configuration of aterminal according to Embodiment 1;

FIG. 4 is a block diagram illustrating the configuration of the basestation according to Embodiment 1;

FIG. 5 is a block diagram illustrating the configuration of the terminalaccording to Embodiment 1;

FIG. 6 is a sequence diagram illustrating an operation example of thebase station and the terminal according to Embodiment 1;

FIG. 7A is a diagram illustrating exemplary cases of CORSETs accordingto Configuration Example 1 of Embodiment 1;

FIG. 7B is a diagram illustrating a configuration example of the CORSETsaccording to Configuration Example 1 of Embodiment 1;

FIG. 8A is a diagram illustrating exemplary cases of CORSETs accordingto Configuration Example 2 of Embodiment 1; and

FIG. 8B is a diagram illustrating a configuration example of the CORSETsaccording to Configuration Example 2 of Embodiment 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a detailed description will be given of embodiments of thepresent disclosure with reference to the accompanying drawings.

[Assumptions of CORSETs]

As illustrated in FIGS. 1A and 1B, the following situations are assumed:multiple CORSETs to be mapped are divided from each other in thefrequency domain (Frequency Division Multiplexing: FDM); CORSETs aredivided from each other in the time domain (Time Division Mulitplexing:TDM); and CORSETs overlap with each other in the frequency domain or thetime domain or both.

In addition, each CORSET contains multiple control channel elements(CCEs) such as CCE #0 to CCE #X.

Mainly, there are two types of CORSETs: CORSET to which a UE-specificcontrol signal is mapped (referred to as “UE specific CORSET”); andCORSET to which a control signal directed to multiple UEs is mapped(referred to as “Group common CORSET”). In a Group common CORSET, forexample, control signals indicating information common to multiple UEs,such as RACH response, power control, paging indication and assignmentof a system information block (SIB) are mapped. These control signalsare the signals mainly mapped to a search space called “common searchspace” in LTE.

Moreover, in a UE specific CORSET, a CCE number applicable to a searchspace where a DCI is monitored by each UE is defined so as to be foundby an ID that identifies the UE (e.g., Radio Network TemporaryIdentifier (RNTI) or a slot number), for example.

In New RAT, studies have been carried out on configuring a UE withmultiple CORSETs as described above. The UE monitors a search space inthe multiple CORSETs thus configured in the UE and detects a DCIdirected to the UE.

In this case, however, when a UE monitors multiple CORSETs configured inthe UE in every slot, the number of candidates for PDCCH regions where aDCI is mapped increases, and causes a problem of increase in powerconsumption of the UE or increase in probability of erroneous detection.

In this respect, a description will be hereinafter given of a method inwhich a UE monitors multiple CORSETs and appropriately detects a DCI,and which also reduces the power consumption of the UE and lowers theprobability of erroneous detection.

[Summary of Communication System]

A communication system according to each embodiment of the presentdisclosure includes base station 100 and terminal 200 (UE).

FIG. 2 is a block diagram illustrating part of a configuration of basestation 100 according to an embodiment of the present disclosure. Inbase station 100 illustrated in FIG. 2, DCI generator 102 selects one ofmultiple cases each indicating a combination of CORSETs (or a CORSET) tobe monitored by terminal 200 among multiple control channel regions(CORSETs). Transmitter 106 indicates, by higher-layer signaling,configuration information indicating the multiple cases, and indicatesthe selected case by dynamic signaling.

FIG. 3 is a block diagram illustrating part of a configuration ofterminal 200 according to an embodiment of the present disclosure. Interminal 200 illustrated in FIG. 3, receiver 201 receives higher-layersignaling containing configuration information indicating multiple caseseach indicating a combination of CORSETs (or a CORSET) to be monitoredby terminal 200 among multiple control channel regions (CORSETs) andreceives dynamic signaling indicating one of the multiple cases. DCIreceiver 203 detects control information (DCI) directed to terminal 200of DCI receiver 203 in a CORSET corresponding to the case indicated bydynamic signaling.

Embodiment 1

[Configuration of Base Station]

FIG. 4 is a block diagram illustrating the configuration of base station100 according to Embodiment 1. Base station 100 in FIG. 4 includesCORSET configurator 101, DCI generator 102, error correction encoder103, modulator 104, signal assigner 105, transmitter 106, receiver 107,signal demultiplexer 108, demodulator 109, and error correction decoder110.

CORSET configurator 101 configures each terminal 200 (UE) with a CORSET.The configuration (definition) of a CORSET, for example, contains thenumber of physical resource blocks (PRBs), a PRB number, a symbolnumber, and the number of symbols where each CORSET is mapped, and an IDused in scrambling the CORSET, a mapping method (localized ordistributed) of a resource element group (REG), and information on Quasicollocation (QCL) and/or the like. The configuration of a CORSET may beindicated to terminal 200 by, for example, higher-layer signaling (maybe the signaling identical to the signaling used for case configurationinformation to be described hereinafter or may be different signaling).

Moreover, CORSET configurator 101 determines a combination of CORSETs tobe monitored by terminal 200 among multiple CORSETs configured interminal 200. CORSET configurator 101 then generates higher-layersignaling (system information block (SIB) or dedicated radio resourcecontrol (RRC)) containing information indicating multiple cases eachindicating the determined combination of CORSETs (hereinafter, referredto as “case configuration information”). CORSET configurator 101 outputshigher-layer signaling to error correction encoder 103 and outputs thecase configuration information to DCI generator 102 and signal assigner105.

DCI generator 102 selects (determines), for example, on the basis ofinformation such as the amount of a control signal or the amount of dataper slot (not illustrated), one case corresponding to a CORSET to bemonitored by terminal 200 from among the multiple cases indicated by thecase configuration information received from CORSET configurator 101 andgenerates bit information corresponding to the selected case(hereinafter, may be referred to as “case information”).

The generated case information (bit information) is mapped to, forexample, a group common PDCCH (e.g., see NPL 2), a PDCCH which is mappedto a group common CORSET and can be received by multiple UEs, or acontrol signal that correctively transmits, using one PDCCH, signalsdirected to multiple UEs as in DCI format 3/3A of LTE. These controlsignals are each a DCI that is different from a downlink control signal(DCI) used for indicating DL assignment information or UL assignmentinformation to terminal 200, which will be described hereinafter.

DCI generator 102 outputs a DCI containing case information to signalassigner 105. The control signal containing the case information isgenerated, for example, in every slot or every subframe, and indicatedto terminal 200. Hereinafter, a control signal to be dynamicallyindicated in every slot or every subframe may be referred to as “dynamicsignaling” in order to distinguish the control signal from higher-layersignaling (semi-static indication).

In addition, DCI generator 102 generates a DCI containing resourceallocation information for a downlink (DL) data signal or an uplink (UL)data signal (DL assignment information or UL assignment information) andoutputs the DCI to signal assigner 105. In addition, DCI generator 102outputs the DL assignment information to signal assigner 105 and the ULassignment information to signal demultiplexer 108 from the generatedDCI.

Error correction encoder 103 applies error correction encoding to atransmission data signal (DL data signal) and a higher-layer signaling(case configuration information) received from CORSET configurator 101and outputs the encoded signal to modulator 104.

Modulator 104 applies modulation processing to the signal received fromerror correction encoder 103 and outputs the modulated signal to signalassigner 105.

Signal assigner 105 assigns the signal (DL data signal and/or the caseconfiguration information) received from modulator 104 to a DL resourcebased on the DL assignment information received from DCI generator 102.Moreover, signal assigner 105 maps a DCI to a CORSET corresponding to acase indicated by the DCI received from DCI generator 102 (case selectedby DCI generator 102) (i.e., CORSET to be monitored by terminal 200)among the multiple cases indicated by the case configuration informationreceived from CORSET configurator 101. The transmission signal is formedin the manner described above. The transmission signal thus formed isoutputted to transmitter 106.

Transmitter 106 applies radio transmission processing such asup-conversion to the transmission signal received from signal assigner105 and transmits the resultant signal to terminal 200 via an antenna.

Receiver 107 receives, via the antenna, a signal transmitted fromterminal 200, applies radio reception processing such as down-conversionto the received signal, and outputs the resultant signal to signaldemultiplexer 108.

Signal demultiplexer 108 demultiplexes a UL data signal from thereceived signal received from receiver 106, based on the UL assignmentinformation received from DCI generator 102, and outputs the UL datasignal to demodulator 109.

Demodulator 109 applies demodulation processing to the signal receivedfrom signal demultiplexer 108 and outputs the resultant signal to errorcorrection decoder 110.

Error correction decoder 110 decodes the signal received fromdemodulator 109 to acquire the received data signal (UL data signal)from terminal 200.

[Configuration of Terminal]

FIG. 5 is a block diagram illustrating the configuration of terminal 200according to the present embodiment. In FIG. 5, terminal 200 includesreceiver 201, signal demultiplexer 202, DCI receiver 203, demodulator204, error correction decoder 205, configuration information receiver206, error correction encoder 207, modulator 208, signal assigner 209,and transmitter 210.

Receiver 201 receives the received signal via an antenna, appliesreception processing such as down-conversion to the received signal andthen outputs the resultant signal to signal demultiplexer 202. Thereceived signal contains a DL data signal, higher-layer signaling(containing case configuration information) or dynamic signaling(containing case information), for example.

Signal demultiplexer 202 demultiplexes a signal mapped to a resource towhich the control signal containing the case information may have beenassigned, from the received signal received from receiver 201, andoutputs the demultiplexed signal to DCI receiver 203. Note that, asdescribed above, the case information is mapped to, for example, a groupcommon PDCCH, a PDCCH which is mapped to a group common CORSET and canbe received by multiple UEs, or a control signal that correctivelytransmits, using one PDCCH, signals directed to multiple UEs as in DCIformat 3/3A of LTE (dynamic signaling).

Signal demultiplexer 202 identifies a resource corresponding to a CORSETto be monitored by terminal 200 of signal demultiplexer 202 (CORSET tobe demultiplexed), based on the case information received from DCIreceiver 203 and the information indicating multiple cases (combinationsof CORSETs) and a configuration of each of the CORSETs received fromconfiguration information receiver 206, then demultiplexes the signalmapped to the identified resource, and outputs the signal to DCIreceiver 203. Moreover, signal demultiplexer 202 demultiplexes the DLdata signal or higher-layer signaling from the received signal based onthe DL assignment information received from DCI receiver 203 and outputsthe signal to demodulator 204.

DCI receiver 203 detects the case information from the signal receivedfrom signal demultiplexer 202 (signal mapped to a resource to which thecontrol signal containing the case information may have been assigned)and outputs the detected case information to signal demultiplexer 202.DCI receiver 203 attempts decoding on the signal mapped to the resourcecorresponding to a CORSET, which is received from signal demultiplexer202, and thus detects (receives) a DCI. DCI receiver 203 outputs the ULassignment information indicated by the received DCI to signal assigner209 and outputs the DL assignment information to signal demultiplexer202.

Demodulator 204 demodulates the signal received from signaldemultiplexer 202 and outputs the demodulated signal to error correctiondecoder 205.

Error correction decoder 205 decodes the demodulated signal receivedfrom demodulator 204, outputs the received data signal thus obtained,and outputs the higher-layer signaling thus obtained to configurationinformation receiver 206.

Configuration information receiver 206 identifies a combination ofCORSETs for each terminal 200 and a configuration of each of the CORSETsbased on the case configuration information or CORSET configurationinformation contained in the higher-layer signaling outputted from errorcorrection decoder 205. Configuration information receiver 206 outputsthe identified information to signal demultiplexer 202.

Error correction encoder 207 applies error correction encoding to thetransmission data signal (UL data signal) and outputs the encoded datasignal to modulator 208.

Modulator 208 modulates the data signal received from error correctionencoder 207 and outputs the modulated data signal to signal assigner209.

Signal assigner 209 identifies a resource to which UL data is assigned,based on the UL assignment information received from DCI receiver 203.Signal assigner 209 assigns the data signal received from modulator 208to the identified resource and outputs the resultant signal totransmitter 210.

Transmitter 210 applies transmission processing such as up-conversion tothe signal received from signal assigner 209 and transmits the resultantsignal via the antenna.

[Operations of Base Station 100 and Terminal 200]

Hereinafter, a detailed description will be given of operations of basestation 100 and terminal 200 each configured in the manner describedabove.

FIG. 6 is a sequence diagram illustrating operations of base station 100and terminal 200.

Base station 100 configures CORSETs and multiple cases each indicating acombination of CORSETs to be monitored by terminal 200 (ST 101). Basestation 100 transmits case configuration information indicating themultiple cases thus configured to terminal 200 using higher-layersignaling (ST 102).

Next, base station 100 selects one case corresponding to a CORSET to beactually monitored by terminal 200 from among the multiple casesconfigured in ST 101 (ST 103). Base station 100 then transmits dynamicsignaling containing the case information indicating the selected caseto terminal 200 (ST 104). Base station 100 maps a DCI (such as resourceallocation information) to a CORSET corresponding to the selected case(not illustrated).

Meanwhile, terminal 200 identifies a CORSET to be monitored by thisterminal, based on the case configuration information contained in thehigher-layer signaling received in ST 102 and the case informationcontained in the dynamic signaling received in ST 104 (ST 105). Morespecifically, terminal 200 identifies a CORSET corresponding to the onecase indicated by dynamic signaling among the multiple cases indicatedby the case configuration information, as the CORSET to be monitored bythis terminal.

Terminal 200 monitors the identified CORSET and detects a DCI directedto this terminal (ST 106).

Next, a description will be given of a specific operation exampleaccording to the present embodiment.

Base station 100 configures multiple cases each indicating a combinationof CORSETs to be simultaneously monitored by terminal 200 as follows andindicates the multiple cases using higher-layer signaling (SIB ordedicated RRC).

Case 1: CORSET A

Case 2: CORSET B

Case 3: CORSETs A, B, and C

Case 4: No monitoring

As described above, one case may contain a single CORSET, multipleCORSETs, or No monitoring (monitoring is not performed). In addition,different cases may contain the same CORSET.

Next, base station 100 selects one case corresponding to a CORSET to bemonitored by terminal 200 from among Cases 1 to 4, for example, in everyslot or every subframe (or at every another timing), and indicates theselected case to terminal 200 using two bits contained in dynamicsignaling.

Terminal 200 monitors a CORSET corresponding to the case indicated bydynamic signaling among Cases 1 to 4 indicated by higher-layer signalingand detects a DCI directed to this terminal.

Note that, the following situations are assumed for the dynamicsignaling indicating the case: the dynamic signaling is mapped to agroup common CORSET or to a predetermined resource (e.g., PhysicalControl Format Indicator Channel (PCFICH) of LTE). When the dynamicsignaling is mapped to a group common CORSET, terminal 200 may monitorthe group common CORSET and detect the dynamic signaling indicating thecase. Meanwhile, when the dynamic signaling is mapped to a predeterminedresource, terminal 200 may detect the dynamic signaling on this resourceregardless of mapping of a CORSET.

In this manner, base station 100 can flexibly configure each terminal200 with a CORSET to be monitored by terminal 200, for example, in everyslot or every subframe for each terminal 200. Accordingly, terminal 200needs to monitor only a CORSET corresponding to the case indicated bybase station 100 and does not need to monitor all the CORSETs. Thus,unnecessary monitoring processing for CORSETs otherwise performed byterminal 200 can be prevented, and reduction in the power consumption ofterminal 200 and reduction of erroneous detection can be achieved.

Note that, when the one case selected by base station 100 is indicatedusing a group common PDCCH, or a PDCCH which is mapped to a group commonCORSET and can be received by multiple UEs, base station 100 mayconfigure each terminal 200 with a different CORSET (the number ofCORSETs or combination) corresponding to each case indicated byhigher-layer signaling.

Hereinafter, a description will be given of Configuration Examples 1 and2 of situations where the configuration of a CORSET corresponding toeach case is different for each terminal 200.

Configuration Example 1

FIG. 7A illustrates exemplary CORSETs corresponding to Cases 1 to 4configured for terminals 200 (UEs A, B, and C).

In FIG. 7A, UE A is configured with CORSET A, UE B is configured withCORSETs A and B, and UE C is configured with CORSETs A, B, and C.

In Case 1 of FIG. 7A, each UE monitors one CORSET A.

In Case 2 of FIG. 7A, each UE monitors CORSETs A and B among CORSETsconfigured in each UE. Note that, since UE A is not configured withCORSET B, UE A monitors CORSET A.

In Case 3 of FIG. 7A, each UE monitors CORSETs A, B, and C among CORSETsconfigured in the UE. Note that, since UE A is not configured withCORSET B or C, UE A monitors CORSET A. Meanwhile, since UE B is notconfigured with CORSET C, UE B monitors CORSETs A and B.

In Case 4 of FIG. 7A, each UE does not monitor any CORSET.

When cases are configured in the manner illustrated in FIG. 7A, basestation 100 switches between the cases for each terminal 200 (UE) using,for example, a group common PDCCH or a PDCCH which is mapped to a groupcommon CORSET and which can be received by multiple UEs.

Thus, base station 100 can change the entire amount of CORSETs used formultiple UEs.

As illustrated in FIG. 7B, suppose that CORSETs A, B, and C are mappedin units of symbols, for example.

In this case, when base station 100 indicates Case 1 of FIG. 7A, thenumber of symbols for the CORSET used by all the UEs is one, when basestation 100 indicates Case 2 of FIG. 7A, the number of symbols for theCORSETs used by all the UEs is two, and when base station 100 indicatesCase 3 of FIG. 7A, the number of symbols for the CORSETs used by all theUEs is three.

More specifically, the number of symbols for CORSETs to be used by allthe UEs can be switched in accordance with the case to be indicated.Base station 100 may perform, for example, an operation to indicate Case1 in which the number of symbols of CORSETs is small when the number ofUEs to be connected is small, and to indicate Case 3 in which the numberof symbols for CORSETs is large when the number of UEs to be connectedis large.

Configuration Example 2

FIG. 8A illustrates CORSETs corresponding to Cases 1 to 4 configured interminals 200 (UEs A, B, and C).

In FIG. 8A, UE A is configured with CORSETs A and D, UE B is configuredwith CORSETs B and D, and UE C is configured with CORSETs C and D.

In Case 1 of FIG. 8A, UE A monitors CORSET A but UEs B and C do notmonitor any CORSET.

In Case 2 of FIG. 8A, UE B monitors CORSET B but UEs A and C do notmonitor any CORSET.

In Case 3 of FIG. 8A, UE C monitors CORSET C but UEs A and B do notmonitor any CORSET.

In Case 4 of FIG. 8A, all the UEs monitor CORSET D.

When the cases are configured as illustrated in FIG. 8A, base station100 can change a UE that monitors a CORSET, for example, in every slotor every subframe by switching between the cases for each terminal 200(UE).

As illustrated in FIG. 8B, suppose that CORSETs A, B, and C are mappedin a frequency-multiplexed manner, and CORSET D is mapped in a wideregion containing the frequency domain of CORSETs A, B, and C, forexample.

In this situation, base station 100 may perform an operation such thatbase station 100 indicates a case (any of Cases 1 to 3 in FIG. 8A)corresponding to a UE in connection therewith (UE A, B, or C) when thenumber of UEs in connection therewith is small and indicates Case 4 whenthe number of UEs to be connected is large.

The operation examples have been described thus far.

Note that, although the description has been given above of a situationwhere base station 100 indicates, for each case, CORSETs to besimultaneously monitored by terminal 200, by higher-layer signaling, inaddition to this case, base station 100 may indicate a configuration(definition) of a CORSET to terminal 200 by higher-layer signaling. Thedefinition of a CORSET may be contained in the same signaling as thesignaling that indicates a case for a CORSET or may be indicated asdifferent signaling before the signaling that indicates a case. Thedefinition of a CORSET contains the number of PRBs, a PRB number, asymbol number, and the number of symbols where the CORSET is mapped, andan ID used in scrambling the CORSET, a mapping method (localized ordistributed) of an REG and information on Quasi collocation (QCL),and/or the like.

As described above, in this embodiment, base station 100 indicates, byhigher-layer signaling, case configuration information indicatingmultiple cases each indicating a combination of CORSETs to be monitoredby terminal 200. Base station 100 selects one case used by terminal 200from among multiple cases and indicates the selected case by dynamicsignaling. In other words, indication of a CORSET to be monitored byterminal 200 is made with a combination of higher-layer signaling anddynamic signaling.

Meanwhile, terminal 200 monitors a CORSET corresponding to the caseindicated by dynamic signaling among the multiple cases indicated by thecase configuration information indicated by higher-layer signaling anddetects a DCI (control information) directed to this terminal.

Thus, base station 100 can flexibly change a CORSET to be monitored byterminal 200, for example, in every slot or every subframe by indicatinga case for a CORSET to terminal 200 by dynamic signaling. In addition,for changing a CORSET to be monitored by terminal 200, base station 100may indicate a case using a DCI without indicating a CORSET every time aCORSET is changed. Thus, the signaling overhead for DCIs can be reduced.

Terminal 200 monitors a CORSET corresponding to the case indicated bydynamic signaling, and does not monitor a CORSET not contained in thiscase. Accordingly, terminal 200 does not have to monitor, in every slot,multiple CORSETs configured in terminal 200, so that unnecessarymonitoring of a CORSET can be avoided, and thus the power consumption ofterminal 200 can be reduced, and the probability of erroneous detectioncan be reduced as well.

As described above, according to Embodiment 1, UEs each monitor multipleCORSETs and can appropriately detect a DCI, while the power consumptionof the UEs is reduced and the probability of erroneous detection isreduced as well.

Embodiment 2

Note that, a base station and a terminal according to Embodiment 2include basic configurations common to base station 100 and terminal 200according to Embodiment 1, so that a description will be given whileFIGS. 4 and 5 are incorporated herein.

In Embodiment 2, a description will be given of rules for an operationin a situation where terminal 200 does not receive dynamic signaling(DCI) indicating a case for a CORSET in every slot or every subframe.

Note that, the situation where terminal 200 does not receive a DCIindicating a case for a CORSET is assumed to be, for example, asituation where base station 100 does not transmit a DCI indicating acase for a CORSET, or although the base station transmits a DCIindicating a case for a CORSET, the terminal fails to detect the DCI(misdetection).

Defining the rules for the operation in a situation where terminal 200receives no DCI allows base station 100 to perform, for example, anoperation not to transmit a DCI indicating a case when no change from aspecified value is required. In a situation where the control signalregion for indicating a case is small, base station 100 canadvantageously transmit another signal by not transmitting this DCI.

Hereinafter, a description will be given of Operation Examples 2-1 and2-2 according to Embodiment 2.

Operation Example 2-1

[Option 1]

For a situation where terminal 200 receives no DCI indicating a case fora CORSET, base station 100 separately indicates, by higher-layersignaling, a CORSET to be monitored by this terminal 200.

In higher-layer signaling, in addition to Cases 1 to 4 exemplified abovein Embodiment 1, one case, which is Case 5 for a situation whereterminal 200 receives no DCI (no DCI reception) may be additionallyconfigured below, for example.

Case 1: CORSET A

Case 2: CORSET B

Case 3: CORSETs A, B, and C

Case 4: No monitoring

Case 5 (no DCI reception): CORSET C

Note that, a CORSET of Case 5 is not limited to CORSET C (the sameCORSET as the other cases) and may be another CORSET. In this way, thecase to be used in a situation where terminal 200 receives no DCI can bea case different from the CORSETs of Cases 1 to 4 or the same CORSETs.Thus, a CORSET to be monitored in a situation where terminal 200receives no DCI can be flexibly configured.

Suppose, for example, a situation where base station 100 does nottransmit case information using, as described above, a group commonPDCCH, a PDCCH which is mapped to a group common CORSET and which can bereceived by multiple UEs, or a control signal that collectivelytransmits, using one PDCCH, signals directed to multiple UEs as in DCIformat 3/3A of LTE. In this case, base station 100 may map a DCIcontaining resource allocation information or the like to a CORSETcorresponding to Case 5. Thus, terminal 200 can detect a DCI (resourceallocation information or the like) by monitoring the CORSETcorresponding to Case 5 indicated by higher-layer signaling even in asituation where terminal 200 receives no DCI containing the caseinformation.

[Option 2]

Base station 100 and terminal 200 specify at least one case (e.g.,Case 1) among multiple cases (e.g., Cases 1 to 4 described inEmbodiment 1) indicated by higher-layer signaling to be a CORSET to bemonitored by terminal 200 for a situation where this terminal 200receives no DCI indicating a case for a CORSET.

Accordingly, in a situation where terminal 200 receives no DCIindicating a case for a CORSET, new signaling for indicating a CORSET tobe monitored by this terminal 200 becomes unnecessary in the higherlayer.

When transmitting no case information as described in Option 1, forexample, base station 100 may map a DCI containing resource allocationinformation or the like to the specified CORSET. Accordingly, terminal200 can detect the DCI (resource allocation information or the like) bymonitoring the specified CORSET even in a situation where terminal 200receives no DCI containing the case information.

[Option 3]

Terminal 200 monitors all the CORSETs configured in this terminal in asituation where terminal 200 receives no DCI indicating a case for aCORSET.

Accordingly, even in a situation where terminal 200 fails to receive aDCI although base station 100 transmits the DCI indicating a case for aCORSET, monitoring all the CORSETs by terminal 200 increases thepossibility for terminal 200 to successfully receive another DCIdirected to this terminal 200.

[Option 4]

Terminal 200 monitors a specified CORSET in a situation where terminal200 receives no DCI indicating a case for a CORSET.

In a situation where terminal 200 receives no DCI indicating a case fora CORSET, for example, terminal 200 may monitor a group common CORSET, aCORSET having the smallest CORSET number, or a CORSET having thesmallest symbol number among the symbols to which CORSETs are mapped.Note that, the CORSET with the smallest CORSET number may be set to be agroup common CORSET.

For a situation where base station 100 does not transmit caseinformation as described in Option 1, for example, base station 100 maymap a DCI containing resource allocation information or the like to aspecified CORSET. Thus, even in a situation where terminal 200 receivesno DCI containing case information, terminal 200 can detect a DCI(resource allocation information or the like) by monitoring thespecified CORSET.

Note that, when monitoring a group common CORSET in a situation whereterminal 200 receives no DCI containing case information, terminal 200may monitor a group common CORSET for only a DCI for shared informationdirected to multiple UEs such as RACH response, power control, pagingindication and assignment of an SIB or may also monitor a UE specificDCI.

Accordingly, in a situation where terminal 200 receives no DCIindicating a case for a CORSET, the number of CORSETs to be monitored bythis terminal 200 can be suppressed to be small or to a small region.Furthermore, when a CORSET having the smallest symbol number is set tobe the CORSET to be monitored by terminal 200 in a situation whereterminal 200 receives no DCI indicating a case for a CORSET, the numberof symbols to which no data can be assigned by a control signal can bereduced.

The CORSET to be monitored by terminal 200 in a situation where terminal200 receives no DCI indicating a case for a CORSET is not limited to agroup common CORSET, a CORSET having the smallest CORSET number, or aCORSET having the smallest symbol number among the symbols to whichCORSETs are mapped.

[Option 5]

For a situation where terminal 200 receives no DCI indicating a case fora CORSET in a slot or a subframe, terminal 200 configures a CORSET to bemonitored, in accordance with a type of this slot or subframe.

The type of slot or subframe mentioned herein refers to a slot orsubframe for UL, DL, or other purposes (slots that switch between DL andUL, D2D, MTC, eIMTA, and URLLC, for example). In addition, the type ofslot or subframe may be defined as the number of DL symbols (DL length)in a slot or a subframe.

Combinations of types of slots or subframes with CORSETs to be monitoredby terminal 200 may be configured as follows:

DL slot: CORSETs A and B

UL centric slot: CORSET B

Only UL slot: No monitoring

UL/DL switching slot: CORSET C

Note that, the term “UL centric slot” refers to a slot in which a DLcontrol signal is mapped to a forward part of the slot and UL data or acontrol signal is mapped to a rearward part of the slot. Moreover, theterm “only UL slot” refers to a slot in which all the symbols of theslot are assigned to UL.

More specifically, a large number of CORSETs is configured in DL slotsbecause the number of symbols to which a DL control signal is mapped islarge in these slots, while a small number of CORSETs is configured inUL centric slots or UL/DL switching slots because the number of symbolsto which a DL control signal is mapped is small in these slots ascompared with DL slots. Meanwhile, since there are no symbols to which aDL control signal is mapped in only UL slots, “No monitoring” isconfigured these slots.

Furthermore, the configuration of a CORSET to be monitored in asituation where terminal 200 fails to receive a DCI indicating a casefor a CORSET may be indicated by higher-layer signaling or may bespecified.

In addition, it is also possible to switch between Options 1 to 4described above in accordance with the type of slot or subframe.Moreover, it is also possible to switch between Cases 1 to 4 describedin Embodiment 1, in accordance with the type of slot or subframe.

Accordingly, terminal 200 can change a CORSET to be monitored, inaccordance with the type of slot or subframe. This is effective, forexample, when the amount of a CORSET required varies in accordance withthe type of slot or subframe.

In a situation where terminal 200 fails to receive a DCI although basestation 100 transmits the DCI indicating a case for a CORSET, forexample, terminal 200 can estimate, in accordance with the type of slotor subframe, a CORSET used by base station 100 for indicating the DCI,so that the probability of terminal 200 successfully receiving anotherDCI directed to this terminal 200 increases.

Moreover, when not transmitting case information as described in Option1, for example, base station 100 may map a DCI containing resourceallocation information or the like to a CORSET corresponding to the typeof slot or subframe. Accordingly, even in a situation where terminal 200receives no DCI containing case information, terminal 200 can detect aDCI (resource allocation information or the like) by monitoring theCORSET corresponding to the slot or subframe.

Options 1 to 5 of Operation Example 2-1 have been described thus far.

Operation Example 2-2

In terminal 200, there may be a configuration with which terminal 200receives no dynamic signaling containing case information of a CORSET(group common PDCCH, a PDCCH which is mapped to a group common CORSETand which can be received by multiple UEs, or a control signal thatcollectively transmits, using one PDCCH, signals directed to multipleUEs as in DCI format 3/3A of LTE) in any slot or subframe.

In particular, configuring terminal 200 to receive multiple DCIs whenreception quality of terminal 200 is poor causes a large amount ofresources occupied by DCIs. Moreover, when reception quality of terminal200 is poor, the probability of erroneous detection or of misdetectionin which terminal 200 fails to correctly receive a DCI increases.

In this respect, base station 100 may assign a UE with poor receptionquality to a group different from a group of UEs with good receptionquality and configure the group to which the UEs with poor receptionquality belong, not to receive dynamic signaling indicating a case for aCORSET.

When terminal 200 is configured not to receive dynamic signalingcontaining case information of a CORSET, for example, Option 3 or 5described in Operation Example 2-1 may be applied. Thus, althoughterminal 200 receives no case information, terminal 200 monitors aCORSET to which a DCI (resource allocation information or the like)directed to this terminal may have been mapped, and thus can detect aDCI.

Operation Examples 2-1 and 2-2 according to Embodiment 2 have beendescribed thus far.

As described above, for a situation where base station 100 is configurednot to transmit dynamic signaling (e.g., such as a group common PDCCH)indicating a case for a CORSET in every slot or every subframe or for asituation where terminal 200 fails to receive dynamic signaling althoughbase station 100 transmits dynamic signaling indicating a case for aCORSET in every slot or every subframe, terminal 200 monitors a searchspace in multiple CORSETs thus configured and can appropriately detect aDCI.

Embodiments of this disclosure have been described thus far.

Note that, in the embodiments described above, a description has beengiven of the situation where four cases are indicated by higher-layersignaling while a case is indicated using two bits contained in a DCI,but the present disclosure is not limited to this case, and the numberof cases to be indicated by higher-layer signaling may be a number otherthan four, a case may be indicated using more than two bits contained ina DCI, and two cases may be indicated using one bit.

Furthermore, in the above embodiments, as to the frequency domain (PRB#), physical mapping has been described as an example, but the presentdisclosure can be applied to logical mapping as well. In the case oflogical mapping, the logical mapping is changed to physical mapping, sothat the frequency domain that is contiguous in logical mapping ismapped to physically distant positions. Thus, the frequency diversityeffect can be obtained in this case.

Moreover, the DCI described above may be transmitted on a PDCCHtransmitted at the time of data assignment for terminal 200 (UE)(UE-specific DCI) or on another PDCCH transmitted with a group commoncontrol resource set. In a situation where the DCI is transmitted on agroup common PDCCH, since multiple UEs receive the same configuration,overhead can be reduced. Moreover, when the DCI is transmitted onindividual PDCCHs, individual configurations can be set for terminals,respectively. Moreover, the DCI may be transmitted on another resourcewithout limitation to a group common resource set and a UE specificcontrol resource set.

Moreover, a group common PDCCH may be defined using a different termsuch as Physical Control Format Indicator Channel (PCFICH), PhysicalSlot Format Indicator Channel (PSFICH), or PDCCH type 0.

Moreover, a group common control resource set may be called a commoncontrol resource set, a group common search space, or a common searchspace.

Moreover, the higher-layer signaling may be replaced with MAC signaling.In case of MAC signaling, the frequency of changing the case configuredin a UE can be increased as compared with RRC signaling.

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in each embodiment may be controlled partly or entirely by thesame LSI or a combination of LSIs. The LSI may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. The LSI may include a data input and output coupledthereto. The LSI herein may be referred to as an IC, a system LSI, asuper LSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit, a general-purpose processor, or a special-purposeprocessor. In addition, a Field Programmable Gate Array (FPGA) that canbe programmed after the manufacture of the LSI or a reconfigurableprocessor in which the connections and the settings of circuit cellsdisposed inside the LSI can be reconfigured may be used. The presentdisclosure can be realized as digital processing or analogue processing.If future integrated circuit technology replaces LSIs as a result of theadvancement of semiconductor technology or other derivative technology,the functional blocks could be integrated using the future integratedcircuit technology. Biotechnology can also be applied.

A base station according to the present disclosure includes: circuitry,which, in operation, selects one of a plurality of cases each indicatinga combination of control channel regions to be monitored by a terminalamong a plurality of control channel regions; and a transmitter, whichin operation, indicates, by higher-layer signaling, configurationinformation indicating the plurality of cases, and indicates theselected case by dynamic signaling.

In the base station according to this disclosure, the transmitterindicates, by the higher-layer signaling, a control channel region for asituation where the dynamic signaling is not received by the terminal,the control channel region being a region to be monitored by theterminal.

In the base station according to this disclosure, a control channelregion to be monitored by the terminal is specified for a situationwhere the dynamic signaling is not received by the terminal.

In the base station according to this disclosure, the specified controlchannel region is at least one of the plurality of control channelregions.

In the base station according to this disclosure, the specified controlchannel region is a control channel region having a smallest controlchannel region number or having a smallest symbol number of a symbolwhere the control channel region is mapped.

In the base station according to this disclosure, the specified controlchannel region is associated with a type of slot in which the dynamicsignaling is not received.

A terminal according to the present disclosure includes: a receiver,which in operation, receives higher-layer signaling containingconfiguration information indicating a plurality of cases eachindicating a combination of control channel regions to be monitored bythe terminal among a plurality of control channel regions, and receivesdynamic signaling indicating one of the plurality of cases; andcircuitry, which, in operation, detects control information directed tothe terminal in the control channel region corresponding to the one caseindicated by the dynamic signaling among the plurality of cases.

A communication method according to this disclosure includes: selectingone of a plurality of cases each indicating a combination of controlchannel regions to be monitored by a terminal among a plurality ofcontrol channel regions; and indicating, by higher-layer signaling,configuration information indicating the plurality of cases, andindicating the selected case by dynamic signaling.

A communication method according to this disclosure includes: receivinghigher-layer signaling containing configuration information indicating aplurality of cases each indicating a combination of control channelregions to be monitored by a terminal among a plurality of controlchannel regions, and receiving dynamic signaling indicating one of theplurality of cases; and detecting control information directed to theterminal in the control channel region corresponding to the one caseindicated by the dynamic signaling among the plurality of cases.

INDUSTRIAL APPLICABILITY

An aspect of this disclosure is useful in mobile communication systems.

REFERENCE SIGNS LIST

-   100 Base station-   101 CORSET configurator-   102 DCI generator-   103, 207 Error correction encoder-   104, 208 Modulator-   105, 209 Signal assigner-   106, 210 Transmitter-   107, 201 Receiver-   108, 202 Signal demultiplexer-   109, 204 Demodulator-   110, 205 Error correction decoder-   200 Terminal-   203 DCI receiver-   206 Configuration information receiver

1. A terminal comprising: a receiver, which, in operation, receives, viahigher-layer signaling, configuration information indicating a pluralityof cases configured per terminal, each of the plurality of casesincluding one or more control channel regions, and receives, via bydynamic signaling, information indicating one case out of the pluralityof cases; and circuitry, which in operation, monitors a control channelin the one or more control channel regions included in the one case. 2.The terminal according to claim 1, wherein the one or more controlchannel regions to be monitored by the terminal where the dynamicsignaling is not received by the terminal is indicated by thehigher-layer signaling.
 3. The terminal according to claim 1, whereinthe one or more control channel regions to be monitored by the terminalwhere the dynamic signaling is not received by the terminal isspecified.
 4. The terminal according to claim 3, wherein the specifiedone or more control channel regions are included in one of the pluralityof cases.
 5. The terminal according to claim 1, wherein the higher-layersignaling is a Radio Resource Control (RRC) signaling, and the dynamicsignaling is a downlink control information signaling in a PhysicalDownlink Control Channel (PDCCH).
 6. The terminal according to claim 1,wherein the higher-layer signaling is a dedicated Radio Resource Control(RRC) signaling.
 7. The terminal according to claim 1, wherein the oneor more control channel regions included in each of the plurality ofcases is configured per terminal.
 8. The terminal according to claim 1,wherein the information indicating the one case is received using aPhysical Downlink Control Channel (PDCCH) for a plurality of terminals.9. The terminal according to claim 1, wherein the information indicatingthe one case is received using a group common Physical Downlink ControlChannel (PDCCH), group common CORESET, or common search space.
 10. Acommunication method terminal comprising: receiving, via higher-layersignaling, configuration information indicating a plurality of casesconfigured per terminal, each of the plurality of cases including one ormore control channel regions; receiving, via by dynamic signaling,information indicating one case out of the plurality of cases; andmonitoring a control channel in the one or more control channel regionsincluded in the one case.
 11. The communication method according toclaim 10, wherein the one or more control channel regions to bemonitored by the terminal where the dynamic signaling is not received bythe terminal is indicated by the higher-layer signaling.
 12. Thecommunication method according to claim 10, wherein the one or morecontrol channel regions to be monitored by the terminal where thedynamic signaling is not received by the terminal is specified.
 13. Thecommunication method according to claim 12, wherein the specified one ormore control channel regions are included in one of the plurality ofcases.
 14. The communication method according to claim 10, wherein thehigher-layer signaling is a Radio Resource Control (RRC) signaling, andthe dynamic signaling is a downlink control information signaling in aPhysical Downlink Control Channel (PDCCH).
 15. The communication methodaccording to claim 10, wherein the higher-layer signaling is a dedicatedRadio Resource Control (RRC) signaling.
 16. The communication methodaccording to claim 10, wherein the one or more control channel regionsincluded in each of the plurality of cases is configured per terminal.17. The communication method according to claim 10, wherein theinformation indicating the one case is received using a PhysicalDownlink Control Channel (PDCCH) for a plurality of terminals.
 18. Thecommunication method according to claim 10, wherein the informationindicating the one case is received using a group common PhysicalDownlink Control Channel (PDCCH), group common CORESET, or common searchspace.